In a medium saucepan, combine the unsweetened cocoa powder, granulated sugar, and kosher salt. Whisk them together until well blended.
Gradually pour in the cold water while continuing to whisk. This helps to prevent lumps from forming in your mixture.
Place the saucepan over medium heat. Stir the mixture frequently until it comes to a gentle boil. This will take about 5-7 minutes.
Once boiling, reduce the heat and let the syrup simmer for about 5 minutes. Keep stirring occasionally. The syrup will begin to thicken during this time.
After simmering, remove the saucepan from heat and stir in the pure vanilla extract. Mix well to incorporate the flavors.
Allow the syrup to cool slightly before transferring it into a glass jar or bottle. Once it’s cooled completely, seal it tightly and store it in the refrigerator.
